AU2004306122A1 - A matched filter for scalable spread spectrum communications systems - Google Patents
A matched filter for scalable spread spectrum communications systems Download PDFInfo
- Publication number
- AU2004306122A1 AU2004306122A1 AU2004306122A AU2004306122A AU2004306122A1 AU 2004306122 A1 AU2004306122 A1 AU 2004306122A1 AU 2004306122 A AU2004306122 A AU 2004306122A AU 2004306122 A AU2004306122 A AU 2004306122A AU 2004306122 A1 AU2004306122 A1 AU 2004306122A1
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- AU
- Australia
- Prior art keywords
- spread spectrum
- spectrum communications
- recited
- communications system
- matched filter
- Prior art date
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- 238000004891 communication Methods 0.000 title claims abstract description 27
- 238000001228 spectrum Methods 0.000 title claims abstract description 23
- 230000002596 correlated effect Effects 0.000 claims 2
- 238000012545 processing Methods 0.000 abstract description 10
- 238000011084 recovery Methods 0.000 abstract description 4
- 238000000034 method Methods 0.000 description 10
- 238000010586 diagram Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/10—Code generation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0022—PN, e.g. Kronecker
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/709—Correlator structure
- H04B1/7093—Matched filter type
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
- H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
- H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
- H04B2201/70703—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation using multiple or variable rates
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
- H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
- H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
- H04B2201/70707—Efficiency-related aspects
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Noise Elimination (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
- Filters That Use Time-Delay Elements (AREA)
- Optical Communication System (AREA)
- Transmitters (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
- Superheterodyne Receivers (AREA)
Abstract
A spread spectrum communications system using long, scalable PN sequences to achieve variable communication rates using a low-complexity and scalable matched filter architecture to provide a large processing gain, robust recovery of multiple devices in long reach, high ambient-noise environments.
Description
WO 2005/031989 PCT/US2004/031527 1 A MATCHED FILTER FOR SCALABLE SPREAD SPECTRUM COMMUNICATIONS SYSTEMS 5 Background of Invention Field of the Invention. This invention relates to spread spectrum communications. More specifically, this invention relates a filter and use of long, scalable, separable PN sequences to achieve variable communication rates together with low complexity 10 in spread spectrum communications. Description of Related Art. A variety of spread spectrum communications systems are well known in the art. Often these systems use very long PN codes to achieve processing gain. However, typically, such prior systems have substantial problems 15 with coherence and frequency error and such problems interfere with achieving the objective of robust spread spectrum communications. Typically, these prior systems also require large matched filters to despread signals, where the use of correlators is inappropriate. 20 Although the following cited U.S. patent documents are not necessarily "prior art," the reader is referred to the following U.S. patent documents for general background material. Each of these patents is hereby incorporated by references in its entirety for the material contained therein.
WO 2005/031989 PCT/US2004/031527 2 U.S. Patent Nos.: 4,351,064; 4,953,178; 4,977,578; Re. 33,875; 5,319,672; 5,400,359; 5,471,509; 5,737,368; 5,740,096; 5,790,588; 5,790,590; 5,815,055; 5,881,099; 5,909,461; 5,912,644; 5,926,512; 5,974,082; 5,991,332; 6,031,415; 6,104,746; 6,128,332; 6,154,482; 6,154,487; 6,212,219; 6,233,272; 6,265,807; 5 6,317,452; 6,331,998; 6,333,925; 6,356,555; 6,434,185; 6,493,334; 6,493,376; 6,549,567; 6,556,621; 6,560,270; 6,560,271; 6,567,017; 6,570,865; 6,580,750; and 6,590,881. Summary of Invention 10 It is desirable to provide a method and system for the use of long, scalable PN sequences in long distance spread spectrum communications systems. Moreover it is also desirable to provide a low-complexity matched filter architecture that provides robust recovery of multiple devices in a long reach, high ambient noise environments. 15 Accordingly, is an object of this invention to provide a method and system for long distance spread spectrum communications systems that makes use of long scalable PN sequences. Moreover, it is an object of this invention to facilitate operation in high ambient noise environments, by increasing processing gain, to thereby provide the 20 capability to trade off data rate for increased robustness in such high ambient noise environments.
WO 2005/031989 PCT/US2004/031527 3 Another object of this invention is to provide a method and system for long distance spread spectrum communications system that includes a matched filter with reduced complexity that allows robust recovery of multiple devices in long reach, high ambient noise environments. 5 A further object of this invention is to provide a method and system for long distance spread spectrum communications systems that provides for scalable data rates. A still further object of this invention is to provide a method and system for long distance spread spectrum communications systems that does not require the locking of the 10 receiver to an individual client device. A still further object of this invention is to provide a method and system for scaling the complexity of the receiver, including the matched filter structure, to receive and demodulate transmissions from devices possessing very different frequency 15 tolerances. Another further object of this invention is to provide a method and system for determining the time-of-arrival of a received signal. 20 Additional objects, advantages, and other novel features of this invention will be set forth in part in the description that follows and in part will become apparent to those of ordinary skill in the art upon examination of the following, or may be learned with the practice of the invention as described herein. The objects and advantages of this WO 2005/031989 PCT/US2004/031527 4 invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. Still other objects of the present invention will become readily apparent to those skilled in the art from the following description wherein there is shown and described the preferred embodiment 5 of the invention, simply by way of illustration of one of the modes best suited to carry out this invention. As it will be realized, this invention is capable of other different embodiments, and its several details and specific circuits are capable of modification in various aspects without departing from the invention. Accordingly, the objects, drawings and descriptions should be regarded as illustrative in nature and not as 10 restrictive. Brief Description of Drawin2s The accompanying drawings incorporated in and forming a part of the specification, 15 illustrate present preferred embodiments of the invention. Some, although not all, alternative embodiments are described in the following description. Inthe drawings: Figure 1 is a system block diagram showing the major components of one preferred embodiment of the invention. 20 Figure 2 is a detailed block diagram of the matched filter architecture of one preferred embodiment of the method of this invention.
WO 2005/031989 PCT/US2004/031527 5 Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Detailed Description 5 This invention is a filter designed specifically for scalable spread spectrum communications systems and cooperative techniques for the use of long, scalable Pseudo-Noise ("PN") sequences for variable communication rates. Link distance and performance margins in spread spectrum communications can be increased by 10 increasing processing gain. Processing gain is itself directly related to the length of the PN code employed. For example, where the data rate is constrained to one bit per PN sequence, a PN code length of 1000 yields a processing gain of 30 dB, while a PN code length of 10,000 yields a processing gain of 40 dB. In the present invention, long, scalable PN sequences are used with a low-complexity matched filter 15 architecture to provide variable communication rates, robust recovery of multiple devices in ordinary-as well high ambient noise operating environments. In the present invention sites may receive signals, simultaneously or near simultaneously, from a multitude of transmitting devices. Each of these received signals will typically have a corresponding frequency error. Furthermore, the frequency error of the devices may 20 be very different depending on system design objectives, which may be selected to optimize the tradeoffs between variables such as system quality, complexity, cost, and service "class" of the devices. These system requirements tend to preclude locking the receiver to an individual transmitting "client" device in order to achieve frequency WO 2005/031989 PCT/US2004/031527 6 coherence across long PN sequences. This invention addresses this problem with a receiver architecture designed so as to facilitate the "simultaneous" receipt of signals, with a wide range of data rates and a wide range of frequency errors, from a variety of devices. 5 Referring now to figure 1 shows a system block diagram illustrating the major components of one preferred embodiment of the invention. Data bits 100 are spread 101 by a variable length PNA code 102. Typically, this spread 101 operates to spread the data 100 from 1 to 1023 chips, although in alternative embodiments the spread 10 may be varied without departing from the concept of this invention. The resulting chips 106 are further spread 103 by a fixed length PNB code 104. In the present preferred embodiment of the invention, a chipping rate of 5M CPS is used, further scaling the data rates from 19.608 kbps to 38 bits/second, providing processing gains of from 24 dB to 51 dB, respectively, depending on the application requirements and 15 the available signal-to-noise ratio in the available link (communication channel). The resulting spread data is transmitted, typically using a radio transmitter 105 for use with an RF link. Table 107 shows the performance of a variety of PNA code lengths. As can be seen, with a constant chip rate, here 5M CPS, as the PNA code length is increased from 1 to 511, the chips per bit increase from 255 to 130305, the processing 20 gain increases from 24 dB to 51 dB and the data rate is reduced from 19608 to 38 bps. Typically, the length of the fixed length PNB code is designed to be short enough to ensure that the worst case frequency error plus the Doppler shift will cause no more WO 2005/031989 PCT/US2004/031527 7 than 180 degrees of phase roll, or a correlation loss in the first matched filter of approximately 4 dB. Figure 2 shows a detailed block diagram of the matched filter architecture of one 5 preferred embodiment of the method of this invention. The receiver portion of the present data link of this invention includes a radio receiver 201. The output 202 of the receiver 201 provides I & Q channels, which are first processed by a matched filter 203. The matched filter 203 uses the PNB codes as coefficients. Because the frequency can be rolling as much as plus or minus one-hundred eighty degrees across 10 a single PNB code length, a bank of frequency shifters 204, 205, 206, 207, 208, 209, 210, 211 are used prior to sending the filtered data 222 through the PNA matched filters 212, 213,214, 215,216, 217, 218, 219,220. Although, in this figure 2 eight frequency shifters and nine matched filters are shown, the number of each actually employed in a particular embodiment of the invention is dependent on the worst-case 15 frequency roll and the allowable phase error across the concatenated PN codes. The frequency shifters 204, 205,206, 207, 208, 209, 210, 211 perform a complex frequency shift. The matched filters 212, 213, 214, 215, 216, 217,218, 219,220 receive data from the frequency shifters 204, 205, 206, 207, 208, 209, 210, 211 and the matched filter 203 and provide a filtered output signal received by the 20 equalizer/decoder 221. The equalizer/decoder 221 examines the outputs of each matched filter 212, 213, 214, 215, 216, 217, 218, 219, 220 and determines the frequency shift of the received signal and appropriately selects the set of most advantageous signals.
WO 2005/031989 PCT/US2004/031527 8 It is also notable that two smaller matched filters, rather than one large filter is used presently to despread the spread signal. This means, that in the preferred embodiment of this invention, a single long matched filter can be avoided, thereby considerably 5 reducing the amount of signal processing hardware that is required. The described embodiment of this invention is to be considered in all respects only as illustrative and not as restrictive. Although specific steps and associated formulas are provided, the invention is not limited thereto. The scope of this invention is, 10 therefore, indicated by the claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.
Claims (8)
- 2. A spread spectrum communications system, as recited in claim 1, wherein said first pseudo noise source provides a variable length code sequence.
- 3. A spread spectrum communications system, as recited in claim 1, wherein said 15 second pseudo noise source provides a fixed length code sequence.
- 4. A spread spectrum communications system, as recited in claim 1, wherein said first multiplexer mixer spreads said data from said data source with a variable PN code. 20
- 5. A spread spectrum communications system, as recited in claim 1, wherein said second multiplexer mixer spreads said data from said first mixer with a fixed length PN code. WO 2005/031989 PCT/US2004/031527 11
- 6. A spread spectrum communications system, as recited in claim 1, wherein said first matched filter further comprises a set of coefficients correlated to said second pseudo noise source. 5
- 7. A spread spectrum communications system, as recited in claim 1, wherein said plurality of phase/frequency shifters are offset from each other by one or more degrees. 10 8. A spread spectrum communications system, as recited in claim 1, wherein said second matched filters are correlated to said first pseudo noise source.
- 9. A spread spectrum communications system, as recited in claim 1, wherein said first and said second pseudo noise sources may be scaled to longer or shorter fixed or 15 variable code lengths to optimize variables such as connection quality, system complexity, overall implementation cost and service "classes" of devices.
- 10. A spread spectrum communications system, as recited in claim 1, wherein said equalizer/decoder selects an advantageous set of signals from said received signals 20 from said plurality of phase/frequency shifters.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/670,708 US7092426B2 (en) | 2003-09-24 | 2003-09-24 | Matched filter for scalable spread spectrum communications systems |
US10/670,708 | 2003-09-24 | ||
PCT/US2004/031527 WO2005031989A2 (en) | 2003-09-24 | 2004-09-24 | A matched filter for scalable spread spectrum communications systems |
Publications (2)
Publication Number | Publication Date |
---|---|
AU2004306122A1 true AU2004306122A1 (en) | 2005-04-07 |
AU2004306122B2 AU2004306122B2 (en) | 2010-01-28 |
Family
ID=34393448
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
AU2004306122A Ceased AU2004306122B2 (en) | 2003-09-24 | 2004-09-24 | A matched filter for scalable spread spectrum communications systems |
Country Status (8)
Country | Link |
---|---|
US (3) | US7092426B2 (en) |
EP (1) | EP1668782B1 (en) |
JP (1) | JP4600779B2 (en) |
KR (1) | KR20060093700A (en) |
AT (1) | ATE448603T1 (en) |
AU (1) | AU2004306122B2 (en) |
DE (1) | DE602004024096D1 (en) |
WO (1) | WO2005031989A2 (en) |
Families Citing this family (9)
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US7092426B2 (en) | 2003-09-24 | 2006-08-15 | S5 Wireless, Inc. | Matched filter for scalable spread spectrum communications systems |
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US7310064B2 (en) * | 2004-04-29 | 2007-12-18 | Novariant Inc. | Rebroadcasting method and system for navigation signals |
JP4234667B2 (en) * | 2004-11-30 | 2009-03-04 | 株式会社東芝 | OFDM receiver for mobile |
US8364185B2 (en) * | 2005-04-18 | 2013-01-29 | Samsung Electronics Co., Ltd. | Method and system for synchronizing a clock for an adjacent network to a clock for an overlay network |
US7606288B2 (en) * | 2005-05-27 | 2009-10-20 | S5 Wireless, Inc. | Burst spread spectrum radio system and method for asset tracking and data telemetry |
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US8433283B2 (en) | 2009-01-27 | 2013-04-30 | Ymax Communications Corp. | Computer-related devices and techniques for facilitating an emergency call via a cellular or data network using remote communication device identifying information |
US10362270B2 (en) * | 2016-12-12 | 2019-07-23 | Dolby Laboratories Licensing Corporation | Multimodal spatial registration of devices for congruent multimedia communications |
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-
2003
- 2003-09-24 US US10/670,708 patent/US7092426B2/en active Active
-
2004
- 2004-09-24 KR KR1020067005749A patent/KR20060093700A/en not_active Application Discontinuation
- 2004-09-24 WO PCT/US2004/031527 patent/WO2005031989A2/en active Application Filing
- 2004-09-24 JP JP2006528267A patent/JP4600779B2/en not_active Expired - Fee Related
- 2004-09-24 EP EP04789059A patent/EP1668782B1/en not_active Not-in-force
- 2004-09-24 DE DE602004024096T patent/DE602004024096D1/en active Active
- 2004-09-24 AU AU2004306122A patent/AU2004306122B2/en not_active Ceased
- 2004-09-24 AT AT04789059T patent/ATE448603T1/en not_active IP Right Cessation
-
2006
- 2006-06-28 US US11/427,256 patent/US7280579B2/en not_active Expired - Fee Related
-
2007
- 2007-09-04 US US11/849,944 patent/US7539235B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
US20060245481A1 (en) | 2006-11-02 |
US7539235B2 (en) | 2009-05-26 |
ATE448603T1 (en) | 2009-11-15 |
US20050074054A1 (en) | 2005-04-07 |
DE602004024096D1 (en) | 2009-12-24 |
KR20060093700A (en) | 2006-08-25 |
EP1668782A4 (en) | 2008-11-12 |
WO2005031989A3 (en) | 2006-01-12 |
EP1668782B1 (en) | 2009-11-11 |
WO2005031989A2 (en) | 2005-04-07 |
US7092426B2 (en) | 2006-08-15 |
JP2007507185A (en) | 2007-03-22 |
JP4600779B2 (en) | 2010-12-15 |
AU2004306122B2 (en) | 2010-01-28 |
US20070291821A1 (en) | 2007-12-20 |
US7280579B2 (en) | 2007-10-09 |
EP1668782A2 (en) | 2006-06-14 |
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